Fig. 5. Effects of N-acetylneuraminic acid (NANA) on nematocyst discharge, adhesive force and tentacle cAMP content. Pre-starved anemones were incubated in filtered, natural sea water containing the specified NANA concentrations for 10min, and in situ adhesive force and nematocyst discharge were measured. Nematocysts on six probes were counted for each dose tested, and the results are the mean of three experiments (, N=3 experiments; n=18 samples). Values of adhesive force measurements were expressed in newtons as the mean of three experiments (, N=3; n=27). For measurement of cAMP, pre-starved anemones were pre-incubated in filtered, natural sea water containing 10^-4moll^-1 IBMX for 20min followed by incubation in sea water containing 10^-4moll^-1 IBMX and different concentrations of NANA for 15min. Individual tentacles were excised, snap-frozen and subsequently assayed for cAMP content of both ectoderm (, N=2; n=20) and endoderm (, N=1; n=10) with 1moll^-1 formic acid, as in Fig.1. Results are expressed as fmolcAMPµg^-1protein. Untreated control values (C) are indicated at the left-hand end of the x-axis. The number of anemones used in each experiment ranged between 16 and 20. Values are means ± S.E.M.